The Gougeon Brothers on Boat Construction - WEST SYSTEM Epoxy

28 Fundamentals of Wood/Epoxy Composite Boatbuilding
desired. WEST SYSTEM 105/207 mixtures resist clouding
in humid conditions and exhibit extremely low blush
formation. 105/207 offers excellent fiberglass wet-out
characteristics and has strong physical properties, so
it can be used as a structural adhesive for gluing and
laminating. It has excellent compatibility with paints
and varnishes. 105/207 cures to a light amber color,
similar to traditional spar varnishes. <strong>The</strong> mix ratio is
three-parts resin to one-part hardener. Pot life at 72°F
(22°C) is 22 to 27 minutes, about the same as 206
Slow Hardener.
209 Extra Slow Hardener is formulated for use
with WEST SYSTEM 105 Resin for general coating and
bonding applications in extremely warm and/or humid
conditions or when extended working time is desired
at room temperature. It provides approximately twice
the working time of 206 Slow Hardener. It forms a
clear, amber-colored solid with good physical properties
and moisture resistance for bonding and coating applications.
<strong>The</strong> mix ratio is three-parts resin to one-part
hardener. Pot life at 72°F (22°C) is 40 to 50 minutes
or 15 to 20 minutes at 95°F (35°C).
WEST SYSTEM Fillers and Additives
Fillers are used to thicken the basic resin/hardener
mixture for specific applications. Each filler possesses
a unique set of physical characteristics, but they can be
generally categorized as either Adhesive (high-density,
high-strength) or Fairing (low-density). Adhesive filler
mixtures cure to a strong, hard-to-sand plastic useful
in structural applications like bonding, filleting, and
hardware bonding. Fairing filler mixtures cure to lightweight,
easily sanded material that is generally used for
cosmetic or surface applications like shaping, filling, or
fairing.
403 Microfibers is a fine fiber blend adhesive filler used
to thicken epoxy to create a multipurpose adhesive that
is especially useful for bonding wood. Epoxy thickened
with 403 has good gap-filling qualities while retaining
excellent wetting/penetrating capability. <strong>The</strong> mixture
cures to an off-white color.
404 High-Density is an adhesive filler developed for
maximum physical properties in hardware bonding
where high-cyclic loads are anticipated. It can also be
Figure 4-2 WEST SYSTEM application tools include mixing
pots, mixing sticks, roller frames, roller covers, roller pans,
glue brushes, spreaders, fillable caulking tubes, and syringes.
used for filleting and gap filling where maximum
strength is necessary. <strong>The</strong> mixture cures to an offwhite
color.
405 Filleting Blend is a strong, wood-toned adhesive
filler, good for use in glue joints and fillets on naturally
finished wood. It mixes easily with epoxy and has good
gap-filling properties. It cures to a dark brown color and
can be used to modify the color of other WEST SYSTEM
filler mixtures.
406 Colloidal Silica is an adhesive filler used to
control the viscosity of the epoxy and prevent epoxy
runoff in vertical and overhead joints. 406 is a very
strong filler that creates a smooth mixture, ideal for
general bonding and filleting. It is also our most versatile
filler. Often used in combination with other fillers,
it can be used to improve the strength, abrasion resistance,
and consistency of fairing compounds, resulting in
a tougher, smoother surface. <strong>The</strong> mixture cures to an
off-white color.
407 Low-Density is a blended microballoon-based
fairing filler used to make fairing putties that are easy
to sand or carve. Mixtures are reasonably strong on a
strength-to-weight basis and cure to a dark red/brown
color.